It is common practice in offshore oil and gas production to have the wellhead and related casing hangers mounted at the ocean floor with the xmas tree and other production equipment mounted above the water level on a production platform. In such situations tieback conductors are use to connect the subsea wellhead equipment to the platform mounted production equipment. In a typical application the high pressure 183/4 inch casing head housing and subsequent casing strings must be tied back to the production platform. It is also desirable at time to provide a means which latches the casing string in position so that once it is seated it does not lift off its seat. Many times it is also preferred that the connector allow the string to pass freely to its seated position without encountering problems of premature setting of the connector.
A preferred connector is one in which the latch allows the threads which it is to engage to pass thereby in a ratcheting fashion so that it is not prematurely set. An example of a prior art connector of this type is shown in U.S. Pat. No. 3,926,457.
U.S. Pat. No. 3,827,488 discloses a ratcheting connector which includes segments having ratchet teeth and backed by resilient pads to allow radial movement of the segments during ratcheting.
U.S. Pat. No. 4,561,499 discloses spring loaded ratchet segments functioning to provide connection between an inner tubular member and an outer tubular member.
Another stab in type of latching mechanism is shown on page 808 of the 1986-87 Composite Catalog of Oil Field Equipment and Services, published by World Oil. The publication states that: "The tieback tool has patented modified wicker threads which engage the square threads of standard casing hangers. The wicker threads are backed up by solid shoulders, and lock with one to two turns of the tieback string."
Other connectors have had such ratcheting engagement but have needed a means to prevent rotation of the latch ring when the string is being rotated to tighten the connection.